This invention relates generally to optical absorption spectroscopy, and more specifically relates to the optical absorption cells utilized in such environments for containing the samples which are subjected to analysis.
In the practice of optical absorption spectroscopy, apparatus such as spectrophotometers are utilized, which include one or more optical paths in which sample or reference materials are inserted, in order that the light absorption characteristics of the materials may be evaluated. The materials to be thus analyzed are physically contained in an optical absorption cell, which typically comprises a small rectangular container, the opposed sides of which are relatively transparent to the wavelengths being utilized during analysis.
Depending upon the nature of the sample being analyzed, it is frequently required that agitation be provided within the absorption cell, in order to maintain a high degree of uniformity. A common arrangement that has been utilized in the past to enable such results incorporates so-called magnetic stirrers. According to this well-known arrangement, a magnetically responsive agitator is positioned at the bottom of the cell container, and is caused to rotate in synchronism with an externally applied rotating magnetic field. In a typical arrangement, the magnetic field may be provided by a bar magnet which is mounted beneath the cell, and rotates about a vertical axis, so that the magnetic poles of the bar magnet substantially rotate in horizontal planes. In this arrangement the magnetic stirring body is itself rotatable about a vertical axes, and includes magnetic poles displaced from its vertical axes so that the stirrer body rotates about its vertical axis in synchronism with the field.
Techniques and apparatus of the foregoing type, while completely adequate for those applications where the optical absorption cells are characterized by a substantially square internal cross-section, have been found to be relatively inacceptable in those instances where the internal cross-section of the cells depart from a square. In particular, there exist numerous instances in the present art, wherein cells of the type known in the art as "micro cells" are utilized for sample evaluation. These cells are characterized by an internal cross-section which remains rectangular, but wherein the first dimension A is much larger than the second dimension B. In these instances, it is either impractical to emplace or operate a magnetic stirring arrangement of the type heretofore discussed, i.e. wherein the stirring body is positioned at the cell bottom and rotates about its vertical axes. Or alternatively (if such a stirring body is indeed positionable and operable) the stirring action, i.e. the agitation of fluidic samples, is found to be inadequate, since only a very small portion of the cell contents are actually subjected to agitation.
In accordance with the foregoing, it may be regarded as an object of the present invention, to provide an improved magnetic stirring arrangement, which enables highly effective agitation of fluidic samples contained in cells of the micro-cell or semi-micro-cell type, i.e. in cells having interior dimensions A .times. B, where A is relatively large compared with B.
It is a further object of the invention, to provide an improved magnetic stirrer body, which may be placed in a micro or semi-micro absorption cell, which body enables highly effective agitation of the fluidic sample contained in such cell, and which body may be actuated by rotating field sources of the type heretofore conventionally utilized in the art.